Device for automatic regulation of the running speed of a drilling turbine through elastic accumulator means

ABSTRACT

Device for automatic regulation of the running speed of a drilling turbine, adapted to compensate for a drop in the pressure power of the drilling fluid through the turbine by an opposite variation of the flow rate of said fluid through the turbine, comprising a tank of elastically expansible volume whereinto is applied the pressure of the drilling fluid, said tank being placed upstream with respect to the turbine, in the vicinity thereof and acting as a flow regulating means.

[ 1 Oct. 23, 1973 [56] References Cited UNITED STATES PATENTS I DEVICE FOR AUTOMATIC REGULATION OF THE RUNNING SPEED OF A DRILLING TURBINE THROUGH ELASTIC ACCUMULATOR MEANS 700700 043044 5 55 oo/ 1 573577 7ll-lll 4 44 mmfl m mm 4 mm m M "knnei beaepl b fl h e e c wC fh SDPT 068088 655666 999999 111111 /////I 26 27 1 1 23 43 267 43 848804 533579 222233 [75] Inventors: Wladimir Tiraspolsky,

lssy-les-Moulineaux; Michel Flamand, Neuilly sur/Seine; Re'mi Reynard, Montesson, all of France lnstitut Francais du Petrole Primary ExaminerJames A. Leppink Dec 2, 1971 Attorney-Paul M. Craig et al.

Appl. No.: 204,283

[73] Assignee:

[22] Filed:

ABSTRACT Related US. Application Data Continuation-impart of Ser. No. 47,318, June 18, 1970, abandoned.

Device for automatic regulation of the running speed of a drilling turbine, adapted to compensate for a drop in the pressure power of the drilling fluid through the turbine by an opposite variation of the flow rate of [30] I Foreign Application Priority Data said fluid through the turbine, comprising a tank of June 27,1969 France...........................6921932 elastically expansible volume whereinto is applied the pressure of the drilling fluid, said tank being placed upstream with respect to the turbine, in the vicinity thereof and acting as a flow regulating means.

2 0 w N 1 4 w 0 5 4 L C s U 2 5 I 2 5 H7 1 W7 4 1 E 0 0 05 ll 4 2" m mh c .r "a "e S m .m e .mF UN 55 13 Claims, 5 Drawing Figures a ll a -%9/////////////////////////////////// PATENTEDUBI 23 W3 SHEET 10F 4 FIG] DEVICE FOR AUTOMATIC REGULATION OF THE RUNNING SPEED OF A DRILLING TURBINE THROUGH ELASTIC ACCUMULATOR MEANS This application is a continuation-in-part of our copending application Ser. No. 47,318, filed on June 18, 1970 for Device for automatic regulation of the running speed of a drilling turbine through elastic accumulator means and now abandoned.

The present development of turbodrilling requires the use of means for automatic regulation of the operating parameters of a drilling turbine.

One of these means consists of providing the turbine with such a blading that the pressure drop through the turbine decreases with a decreasing running speed when the flow rate is kept constant and of varying the turbine feeding rate in inverse ratio to the pressure, whereby additional torque and power are given to the turbine when the running speed decreases.

Such a compensation for the hydraulic power loss by the turbine in the form of pressure drop, may be achieved by use of circulation pump means so as to automatically compensate for the pressure changes by flow rate adjustments, such pumps means being, for example, axial pumps or pumping units driven by Diesel engines and associated with a torque converter.

However the efficiency of such a regulation decreases with increasing depths as, correlatively, the column of drilling pipes or drill string between the pump means and the turbine grows longer, since all the regulation means are operated at the surface and accordingly the compensation for changes of hydraulic pressure by opposite changes of the flow rate of the fluid injected from the surface, requires action on the whole mass of liquid contained in the drill string between the surface and the turbine, which results in a response time which may be very long and accordingly incompatible with a good regulation.

The speed of variation of the operating parameters of a turbine is moreover much higher than the speed of adaptation of the pumps to the new values of these parameters.

Another known solution consists of permanently feeding the turbine at a flow rate in excess to the normal one through a valve so adjusted as to ensure a constant feeding pressure. This system suffers from the drawbacks of a systematic hydraulic power loss corresponding to the portion of the fluid stream which is discharged to the external annular space between the drill string and the borehole wall, without producing any effective power, of an instable regulation rate and of a rapid wear of the working pieces due to the action of the drilling muds.

The solution according to the invention avoids these drawbacks by providing for the flow rate adjustments required to compensate for the turbine pressure changes through a tank arranged in the vicinity of the turbine whereinto is applied the pressure of the drilling fluid. This tank, having an elastically expansible volume, acts as a flow rate regulating capacity, with a short response time.

According to one embodiment of the invention this regulating device is formed of at least one elastic sleeve or sheath associated to a tube or rigid stem whereby is insured the mechanical continuity of the drill string, said sleeve being placed above the drill bit and close to the drilling turbine.

This accumulator sleeve may be fastened internally or externally to the rigid tube. It may be made advantageously of. rubber or any other elastomer or similar material and conveniently reinforced so as to provide for a maximum increase of the stored fluid volume in the range of internal over-pressures corresponding to the running speed of the turbine.

The drilling fluid might also circulate around the accumulator sleeve so that its pressure would apply onto the external wall of the sleeve.

Tests have shown that the variation of such sleeve internal volume, per unit of internal pressure change, generally decreases with an increasing pressure. In order to reduce this inconvenience to a minimum, it may be convenient to realize the sleeve in the form of at least two concentric sheaths, whose elastic characteristics are such that the first sheath has a resilient force balancing the internal pressure force up to the moment where it expands to such an extent as to come into contact with the second sheath and that, from this moment, the tight internal sheath, whose expansion is limited to the surrounding sheath, has the only effect of balancing the already attained pressure, the pressure excess being sustained by the next sheath which will work within a more favorable strain range than if it had to sustain the entire pressure, the mechanism being similar when using more than two sheaths.

Each external sheath, as well as the tube or the rigid stern in the case where it is external to the elastic sheath which is the closest to the axis, will be provided with pressure exchange orifices communicating with the annular space surrounding the drill string or at least with one space at a pressure lower than the minimum feeding pressure of the turbine, so as to make possible the expansion of the sleeve by the effect of the feeding pressure.

According to a preferred embodiment there will be used a sleeve comprising at least one tight armature formed of a helical metal winding, deformable by the effect of the internal pressure acting against antagonistic elastic means.

According to a more particularly preferred embodiment of the invention there will be used at least one elastically deformable sleeve placed in the vicinity of the turbine, so that the pressure of the fluid flowing inside the drill string and that of the fluid flowing outside the drill string through the annular space between said pipe and the wall of the bore hole, be applied respectively on a different side of the sleeve wall. This embodiment combines the advantages of a device with a short response time, due to the location of the regulator sleeve in the vicinity of the turbine, with that of a closed-circuit regulating system. As a matter of fact, a decrease in the pressure of the fluid flowing through the drill string, inside the sleeve, will produce a constriction of the sleeve, resulting in a decrease of its internal volume and accordingly in a corresponding increase of the annular volume between the external wall of the sleeve and the wall of the bore hole. This increase of the annular volume makes it possible to absorb exactly the temporary increase of the flow rate through the turbine, resulting from the additional volume of fluid made available by the constriction of the sleeve, the liquid displacement being effective over only a small length, substantially constant irrespective of the length of the drill string.

The elastic sleeves may be connected rigidly at each end thereof to the tube or rigid stem insuring the mechanical continuity of the drill string. In other embodiments at least one of the ends may undergo an axial displacement while being tightly insulated from the external annular space, so as to follow the length variations of the sleeve accompanying the diameter changes due to the variations of the internal pressure. In such an embodiment the effect of the pressure changes is enhanced by the resulting variation of the axial thrust on the section of the sleeve free end, as well as by the variations of the internal volume of the elastic sleeve accompanying the displacements of said free end.

The described different characteristics may be used, of course, separately or in combination. It would be also possible, without departing from the spirit and scope of the invention, to connect in series, at different levels of the fluid flow, a plurality of groups of concentric elastic sleeves of the above-mentioned type, provided they are all placed in the vicinity of the turbine.

A few non-limitative embodiments are described herebelow, by way of illustrative examples, with reference to the accompanying drawings wherein FIG. 1 is a cross-sectional view of a first embodiment comprising an elastic sheath fastened at both ends inside a rigid tubular envelope,

FIG. 2 shows a variant, wherein the lower end (nearest to the drill bit) of the sheath slides tightly inside the rigid envelope,

FIG. 3 shows a second embodiment comprising two concentric sheaths fastened at their ends inside a rigid tubular envelope,

FIG. 4 shows the preferred embodiment making use of a sleeve deformable against the antagonistic action of elastic means,

FIG. 4A diagrammatically shows a type of sleeve outfitting the device illustrated in FIG. 4.

Referring now to FIG. 1, reference 1 indicates the tubular envelope housing a flexible sleeve or sheath 2. The latter, in the illustrated embodiment, is secured at one end by means of a connector 6, threaded inside the top coupling 3, and terminates at the other end with a shoulder flange 5, fitting with the drill string and which is tightly compressed by screwing of the end coupling 4, between a shoulder 9 of tubular envelope 1 and a compressible tight cushion 7. g

The coupling 4 is connected to the drilling turbine driving the drill bit. Orifices 8 in the tubular envelope 1, provide for a balancing of the respective pressures in the external annular space formed between the elastic sheath 2 and the rigid tube 1. On the left hand side of FIG. 1 the sheath 2 is shown in its expanded position, resulting from the effect of internal pressure.

FIG. 2 shows a variant of this device wherein the lower end of the elastic sheath 2 terminates with a sleeve 11, sliding inside a connector 10 comprising a shoulder 13 limiting the stroke of axial displacement of the sleeve 11. A tight packer, diagrammatically shown as a set of toric joints l2, insures the sealing between the inside of sheath 2 and the annular space between the same and the tube 1.

In this embodiment the pressure changes of the drilling fluid also have an action on the ends 27 and 27' of sleeve 11 in the form of a variation of the axial thrust exerted on said sleeve 11.

Opposed elastic means which may comprise one or more springs or calibrated chokes may be provided in the annular space 28 so as to permit a control of the effect of the fluid pressure variations on sleeve 11.

In the embodiment shown in FIG. 3 there are used two coaxial sleeves l5 and 17, the annular space therebetween being maintained at'a pressure in equilibrium with that of the external annular space, by means of orifices such as 16.

This figure illustrates, by way of example, the case where the ends of the elastic sleeves or sheaths are fixed. The upper end 21 of sheath 15 is tightly pressed by screwing the end seal 23, integral with the upper end of sheath 17, in the top coupling 18, the end seal 23 being provided with grooves for locking and unlocking the same by means of a key.

The lower end 22 of sheath 15 is compressed together with the base portion 23' of sheath 17 by locking the coupling 25 onto the sleeve 19, the sealing at both ends being insured through elastic cushions such as cushions 2 4 and 26.

The structure of the internal tight sheath 17 is so designed that it can counterbalance a given pressure P, corresponding to a degree of expansion at which it comes into contact with sheath 15, as shown on the left-hand side of FIG. 3. If only sheath 17 were present, it would continue to increase in diameter up to the breaking limit without any substantial increase of its specific resistance to internal pressure, but, according to the embodiment shown in FIG. 3, another sheath 15, at this moment, enters in action and its resistance is so calculated that, for the maximum designed pressure P, the external wall of sheath 15 does not come into contact with tube 1. The sheath 15 at this moment will sustain the pressure difference P P P It will therefore work in a range of pressures lower than the total pressure to which a single sheath would have been subjected.

FIG. 4 diagrammatically shows a preferred embodiment of the device according to the invention. In this embodiment the sleeve 2 preferably consists of a metal armature comprising a sealing member,,said armature being formed of at least one helical winding of wires, cables, strands or profiled metal. In FIG. 4A the sleeve 2, shown at a larger scale, comprises two armatures 37 and 38 having opposed winding directions. The sealing is obtained by means of an inner sheath 36 of elastomeric material.

The winding angle a, i.e., the angle formed between each turn of the winding and the axis of sleeve 2 has been chosen lower than the angle 0, insuring the equilibrium of the winding under pressure, which is defined by the following relationship, well known in the art tan 0 2 I and for which the pressure variations to which the sleeve is subjected do not result in any volume variation thereof.

Preferably the winding angle a will be chosen of such a value that the sleeve volume variations be maximum, which value is given by the relationship Accordingly the value of a will be chosen close to'.

The resulting sleeve is deformable but not elastic and there will thus be used an elastic member connected in series with the sleeve 2.

The lower end of the sleeve 2 (FIG. 4) terminates with a collar 5, connected to the drill string, which is tightly compressed by screwing the end connector between a shoulder of the tubular envelope 1 and a compressible tight cushion 7. The upper end of the sleeve 2 is solid with a tubular rigid member 30 slidable along the inner surface of the tubular envelope 1. Gaskets 31 provide for the sealing between the member 30 and the tubular envelope 1.

Elastic means, shown in the drawings as a spring 33, is interposed between a shoulder 34 solid with the tubular member 30 and a shoulder 35 solid with the tubular envelope 1. By this way the spring 33 is connected in series with the sleeve 2.

The operation of the device is as follows By the effect of an increasing difference between the respective pressures applied on each side of the sleeve 2, the armatures 37 and 38 are so distorted that the winding angle of the turns tend towards the equilibrium valueas above defined, which means that angle a increases.

There is thus observed a volume increase of the sleeve and consequently an accumulation of hydraulic fluid in the volume defined by the sleeve.

This volume increase results in an increase in the sleeve diameter and a corresponding decrease in the sleeve length L, by A L.

The upper end of the sleeve 2 moves downwardly, with reference to the drawing, thus driving therewith the tubular member 30 which compresses the spring 33.

When the pressure difference to which the sleeve is subjected decreases, the spring 33 expands and exerts a tractive stress on sleeve 2 which, according to an action opposite to that mentioned above, results in a volume decrease of the sleeve 2 thereby restoring a certain amount of fluid to the drilling turbine.

Such a device has the advantage, by regulating the prestress of spring 33, of determining a minimum pressure value inside the sleeve above which the device according to the invention will perform the automatic regulation of the flow rate feeding the turbine, while the maximum value may be determined either by limiting the maximum compression stroke of the spring, e.g., by means of a stop member limiting the downward motion of the tubular member 30 or by limiting the sleeve diameter increase by abutment of said sleeve against a tubular element of a predetermined inner diameter. The spring compression stroke may be also limited to the maximum value corresponding to the maximum possible expansion of the sleeve by variation of the winding angle a of the turns up to its equilibrium value 0 beyond which the sleeve no longer expands.

From the foregoing description, one skilled in the art easily ascertain the essential characteristics of this invention and, without departing from the spirit and scope thereof, can make various changes and modifications of the invention to adapt it to various usages and conditions. For example the armatures may be constituted by windings of profiled metal strips having a S or Z shaped section, the sealing between the adjacent turns of the winding being achieved by means of suitable joints.

Consequently such changes and modifications are properly, equitably and intended to be within the full range of equivalence of the appended claims.

We claim 1. A device for the automatic regulation of the running speed of a'hydraulic drilling turbine suspended from;the lower end of a drill string, adapted to compensate for a variation of the motive pressure drop of the hydraulic drilling fluid through the turbine by an opposite variation of the flow rate of said fluid through the turbine, said device comprising a tank having at least one deformable wall, said tank defining a volume which varies as a function of the difference between the respective pressures applied on each side of said deformable wall, said tank being directly connected, at one end to the turbine inlet and, at the other end, to the lower end of the drill string, so that the hydraulic drilling fluid flows from the drill string to the turbine through said tank, the inner wall of which is subjected to the drilling fluid pressure, said tank being placed upstream the turbine, in the vicinity thereof and acting as a flow regulating capacity.

'2. A device according to claim 1, wherein said tank is formed of at least one deformable sleeve and in which the mechanical continuity of the drill string is performed by means of a rigid tube of an inner diameter greater than the external diameter of said sleeve and surrounding the latter, said rigid tube connecting the lower end of the drill string to the turbine inlet.

3. A device according to claim 2, wherein the wall of said rigid tube is provided with at least one orifice so as to apply the pressure prevailing in the annular space between the drill string and the wall of the bore hole to the external wall of said sleeve,.the internal wall of which is subjected to the pressure of the drilling fluid prevailing inside the drill string, so that a pressure change, resulting in a corresponding change of the sleeve internal volume and producing a variation in the hydraulic fluid flow rate through the turbine, be accompanied with a change in the volume of said annular space, said volume change being of the same absolute value but opposite to the variation of the sleeve internal volume, and thus adapted to said flow rate change.

4. A device according to claim 2, wherein said deformable sleeve is elastic.

5. A device according to claim 4, wherein said deformable sleeve is made of reinforced elastomer.

6. A device according to claim 4, wherein said sleeve is fastened at both ends to said rigid tube achieving the mechanical continuity of the drill string.

7. A device according to claim 4, wherein at least one end of said sleeve may slide tightly along said rigid tube achieving the mechanical continuity of the drill string.

8. A device according to claim 2, wherein said tank is formed of at least two coaxial elastic sleeves so that the deformation of a first sleeve be limited by abutment of said sleeve against a second sleeve surrounding the first one, said abutment resulting in the transmission to said second sleeve of only a fraction of the drilling fluid pressure prevailing inside said first sleeve.

9. A device according to claim 2, wherein said sleeve is formed of at least one armature comprising elongated elements arranged in at least one helical winding, the turns of which are inclined with respect to the sleeve axis by an acute angle a smaller than the equilibrium acute angle 0 defined by the relationship tan 0 2, and of a sealing member arranged between the turns of said helical winding, said sleeve being secured at one of its ends to said rigid tube connecting the lower end of the drill string to the turbine inlet and further comprising elastic means connecting its other end to said with at least one of the internal and external surfaces of said helical winding.

13. A device according to claim 9, wherein, in the absence of stress, applied to the helical winding, the turns of the helical winding are inclined with respect to the sleeve axis by an angle substantially equal to the acute angle a defined by the relationship tan a 2/7. 

1. A device for the automatic regulation of the running speed of a hydraulic drilling turbine suspended from the lower end of a drill string, adapted to compensate for a variation of the motive pressure drop of the hydraulic drilling fluid through the turbine by an opposite variation of the flow rate of said fluid through the turbine, said device comprising a tank having at least one deformable wall, said tank defining a volume which varies as a function of the difference between the respective pressures applied on each side of said deformable wall, said tank being directly connected, at one end to the turbine inlet and, at the other end, to the lower end of the drill string, so that the hydraulic drilling fluid flows from the drill string to the turbine through said tank, the inner wall of which is subjected to the drilling fluid pressure, said tank being placed upstream the turbine, in the vicinity thereof and acting as a flow regulating capacity.
 2. A device according to claim 1, wherein said tank is formed of at least one deformable sleeve and in which the mechanical continuity of the drill string is performed by means of a rigid tube of an inner diameter greater than the external diameter of said sleeve and surrounding the latter, said rigid tube connecting the lower end of the drill string to the turbine inlet.
 3. A device according to claim 2, wherein the wall of said rigid tube is provided with at least one orifice so as to apply the pressure prevailing in the annular space between the drill string and the wall of the bore hole to the external wall of said sleeve, the internal wall of which is subjected to the pressure of the drilling fluid prevailing inside the drill string, so that a pressure change, resulting in a corresponding change of the sleeve internal volume and producing a variation in the hydraulic fluid flow rate through the turbine, be accompanied with a change in the volume of said annular space, said volume change being of the same absolute value but opposite to the variation of the sleeve internal volume, and thus adapted to said flow rate change.
 4. A device according to claim 2, wherein said deformable sleeve is elastic.
 5. A device according to claim 4, wherein said deformable sleeve is made of reinforced elastomer.
 6. A device according to claim 4, wherein said sleeve is fastened at both ends to said rigid tube achieving the mechanical continuity of the drill string.
 7. A device according to claim 4, wherein at least one end of said sleeve may slide tightly along said rigid tube achieving the mechanical continuity of the drill string.
 8. A device according to claim 2, wherein said tank is formed of at least two coaxial elastic sleeves so that the deformation of a first sleeve be limited by abutment of said sleeve against a second sleeve surrounding the first one, said abutment resulting in the transmission to said second sleeve of only a fraction of the drilling fluid pressure prevailing inside said first sleeve.
 9. A device according to claim 2, wherein said sleeve is formed of at least one armature comprising elongated elements arranged in at least one helical winding, the turns of which are inclined with respect to the sleeve axis by an acute angle Alpha smaller than the equilibrium acute angle theta defined by the relationship tan2 theta 2, and of a sealing member arranged between the turns of said helical winding, said sleeve being secured at one of its ends to said rigid tube connecting the lower end of the drill string to the turbine inlet and further comprising elastic means connecting its other end to said rigid tube, said sleeve being deformable against the antagonistic action of said elastic means.
 10. A device according to claim 9, wherein said elastic means are prestressed.
 11. A device according to claim 9, wherein said elastic means consists of a helical spring.
 12. A device according to claim 9, wherein said sealing means consists of an elastomer sheath in contact with at least one of the internal and external surfaces of said helical winding.
 13. A device according to claim 9, wherein, in the absence of stress, applied to the helical winding, the turns of the helical winding are inclined with respect to the sleeve axis by an angle substantially equal to the acute angle Alpha defined by the relationship tan2 Alpha 2/7. 